1. Field of the Invention
The present invention generally relates to a metallic seal for creating a seal between a pair of members. More specifically, the present invention relates to a seal that provides a highly reliable seal by concentrating the available load over a narrow band (small sealing area equaling high contact stress) to produce a high quality sealing dam over a sufficient width to minimize leakage on a molecular level.
2. Background Information
A typical static seal assembly has a first member with a first mating surface, an annular seal of suitable sealing material (e.g., metal O-ring), and a second member with a second mating surface. A mechanical load is applied to the seal through the first and second mating surfaces of the members. Typically, the mechanical load is created by torquing down a multitude of fasteners such that a displacement, also known as compression, occurs between the sealing surfaces. The net loading of the contact surfaces creates the two sealing lines.
The low leakage requirement can be achieved by compressing a solid metal ring of rectangular cross-section with a sufficient force. One problem with a solid metal ring is that the force created could be of sufficient magnitude to cause plastic deformation of the mating surfaces of the members. This plastic deformation of the mating surface is called brinelling. Once brinelled, the probability of proper re-sealing is drastically reduced without first repairing the damaged sealing surfaces.
The design requirements for static sealing therefore requires an optimum load level and flexibility. A good static seal when compressed must be able to generate load levels large enough to seal, but not large enough to brinell the cavity surface. Currently, there are many types of metallic seals in the prior art.
The metallic xe2x80x9cOxe2x80x9d rings were an early effort to meet these conflicting design requirements. However, the resiliency of this type of seal is rather limited because the xe2x80x9cOxe2x80x9d ring, whether solid or hollow, is usually too stiff, and is inherently expensive. The development of the C-shaped seal was an improvement to the xe2x80x9cOxe2x80x9d ring. In particular, by simply discarding a portion of the xe2x80x9cOxe2x80x9d, the hoop restraint of the seal is greatly reduced and the seal becomes more flexible. However, the basic xe2x80x9cCxe2x80x9d seals typically cannot reach the desirable standard vacuum level of 1xc3x9710exe2x88x929 cc/sec He leakage rate or better without modification and without being coated with very soft plating materials. Some previous C-shaped seals have been designed to provide this level of seal integrity.
In view of the above, it will be apparent to those skilled in the art that there exists a need for an improved seal with optimized sealing areas that minimizes brinelling and shifting of the sealing line. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art once given this disclosure.
One object of the present invention is to provide a highly reliable metallic seal that is relatively inexpensive to manufacture.
Another object of the present invention is to provide a metallic seal, which has geometrically simple cross sections, and can be manufactured with existing equipment in large quantities with tight tolerances.
Still another object of the present invention is to provide a highly reliable metallic seal which concentrates the available load over a narrow band which minimizes the required load to compress the seal by optimizing the sealing dam width.
Yet another object of the present invention is to provide a metallic seal in which the seal dam does not significantly shift during compression of the seal.
Another object of the present invention is to provide a metallic seal, which uses controlled column buckling to limit reaction forces and avoid deformation and brinelling.
Another object of the present invention is to provide a metallic beam column seal which has a leakage rate of less than 1xc3x9710exe2x88x929 cc/sec He leakage rate or better,
The invention results from the realization that a truly superior seal made wholly of metal in the nature of a xe2x80x9cCxe2x80x9d seal can be effected utilizing a construction that has two spaced structured beams interconnected by a structured column which provides an extensive seal and buckles in a controlled fashion to maintain the seal without shifting of the sealing line or brinelling the mating surfaces of the members to be sealed.
The foregoing objects can basically be attained by providing a metallic seal that concentrates the available load over a narrow band to produce a sealing dam over a sufficient width to minimize leakage while optimizing the load required to compress the seal. The metallic seal has a first annular beam section, a second annular beam section, and inner and outer surfaces extending between the first and second annular beam sections. One of the inner and outer surfaces has an annular recess that at least partially defines an annular column section of material extending substantially perpendicular between said first and second annular beam sections thereto. The first annular beam section has a first non-sealing surface and a first raised portion with a first annular sealing surface facing in a first axial direction to contact a first member for creating a first annular sealing dam therebetween. The second annular beam section has a second non-sealing surface and a first raised portion with a second annular sealing surface facing in a second axial direction, which is opposite to the first axial direction, to contact a second member for creating a second annular sealing dam therebetween. The annular inner surface extends between the first and second sealing surfaces to form a central passageway.
Other objects, salient features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.